But I have since removed this code and refreshed, and its still happening.

The page keeps "reloading" (doesnt go blank, you just see the spinning wheel at the top repeatedly). When you scroll to the bottom of the page, you can see the facebook share button disappearing, and reappearing over and over. So basically its the share button that is refreshing itself.

This just randomly started overnight.
It only happens on thread pages from what I can see.
It seems to stop if I am logged out - see the refreshing - then log in and the thread page reloads with me logged in.
But as soon as I navigate (while still logged in) to another thread, the refreshing begins again.

EDIT: After several refreshes it seems to stop (after about a minute of refreshing constantly). This is consistent behavior after several tests.